Conventionally, a vibratory actuator has been known in which an electric field is applied to an actuator body including a piezoelectric element to vibrate the actuator body so that a drive element provided to the actuator body is operated to output driving force. Such vibratory actuators have been used in ultrasonic motors and other apparatuses which are required to move in microstep move.
For example, a vibratory actuator according to PATENT DOCUMENT 1 includes an actuator body including a piezoelectric element, a driver element, provided on the actuator body, for outputting driving force to a movable body, and a pressurizing member for pressing the actuator body from an opposite side to a side of the actuator body at which the driver element is provided. In the vibratory actuator, the actuator body is pressed by the pressurizing member to one (hereinafter referred to as an “abutment body”) of a fixed body and the movable body on which the driver element abuts, and a certain amount of friction force between the driver element and the abutment body is maintained. In this state, an alternating voltage is applied to the piezoelectric element of the actuator body to cause the actuator body to induce vibration, thereby causing the driver element to make an elliptical motion. Thus, increase and reduction of friction force between the driver element and the abutment body are repeated by causing the driver element to make an elliptical motion, so that driving force is output from the driver element to the movable body by friction force when the friction force is increased to drive the movable body in a predetermined direction.
It should be noted that the pressurizing member not only functions to press the actuator body to the abutment body but also functions as a supporting member for supporting the actuator body.